﻿using System;
using System.Runtime.InteropServices;

namespace Shared
{
    public class BrowserHelper
    {
        // For PInvoke: Contains information about an entry in the Internet cache
        [StructLayout(LayoutKind.Explicit, Size=80)]
        public struct INTERNET_CACHE_ENTRY_INFOA
        {
            [FieldOffset(0)]  public uint dwStructSize;
            [FieldOffset(4)]  public IntPtr lpszSourceUrlName;
            [FieldOffset(8)]  public IntPtr lpszLocalFileName;
            [FieldOffset(12)] public uint CacheEntryType;
            [FieldOffset(16)] public uint dwUseCount;
            [FieldOffset(20)] public uint dwHitRate;
            [FieldOffset(24)] public uint dwSizeLow;
            [FieldOffset(28)] public uint dwSizeHigh;
            [FieldOffset(32)] public FILETIME LastModifiedTime;
            [FieldOffset(40)] public FILETIME ExpireTime;
            [FieldOffset(48)] public FILETIME LastAccessTime;
            [FieldOffset(56)] public FILETIME LastSyncTime;
            [FieldOffset(64)] public IntPtr lpHeaderInfo;
            [FieldOffset(68)] public uint dwHeaderInfoSize;
            [FieldOffset(72)] public IntPtr lpszFileExtension;
            [FieldOffset(76)] public uint dwReserved;
            [FieldOffset(76)] public uint dwExemptDelta;
        }

        // For PInvoke: Initiates the enumeration of the cache groups in the Internet cache
        [DllImport(@"wininet",
            SetLastError=true,
            CharSet=CharSet.Auto,
            EntryPoint="FindFirstUrlCacheGroup",
            CallingConvention=CallingConvention.StdCall)]
        public static extern IntPtr FindFirstUrlCacheGroup(
            int dwFlags,
            int dwFilter,
            IntPtr lpSearchCondition,
            int dwSearchCondition,
            ref long lpGroupId,
            IntPtr lpReserved);

        // For PInvoke: Retrieves the next cache group in a cache group enumeration
        [DllImport(@"wininet",
            SetLastError=true,
            CharSet=CharSet.Auto,
            EntryPoint="FindNextUrlCacheGroup",
            CallingConvention=CallingConvention.StdCall)]
        public static extern bool FindNextUrlCacheGroup(
            IntPtr hFind,
            ref long lpGroupId,
            IntPtr lpReserved);

        // For PInvoke: Releases the specified GROUPID and any associated state in the cache index file
        [DllImport(@"wininet", 
            SetLastError=true, 
            CharSet=CharSet.Auto, 
            EntryPoint="DeleteUrlCacheGroup", 
            CallingConvention=CallingConvention.StdCall)]
        public static extern bool DeleteUrlCacheGroup(
            long GroupId,
            int dwFlags,
            IntPtr lpReserved);

        // For PInvoke: Begins the enumeration of the Internet cache
        [DllImport(@"wininet",
            SetLastError=true,
            CharSet=CharSet.Auto,
            EntryPoint="FindFirstUrlCacheEntryA",
            CallingConvention=CallingConvention.StdCall)]
        public static extern IntPtr FindFirstUrlCacheEntry(
            [MarshalAs(UnmanagedType.LPTStr)] string lpszUrlSearchPattern,
            IntPtr lpFirstCacheEntryInfo,
            ref int lpdwFirstCacheEntryInfoBufferSize);

        // For PInvoke: Retrieves the next entry in the Internet cache
        [DllImport(@"wininet",
            SetLastError=true,
            CharSet=CharSet.Auto,
            EntryPoint="FindNextUrlCacheEntryA",
            CallingConvention=CallingConvention.StdCall)]
        public static extern bool FindNextUrlCacheEntry(
            IntPtr hFind,
            IntPtr lpNextCacheEntryInfo,
            ref int lpdwNextCacheEntryInfoBufferSize);

        // For PInvoke: Removes the file that is associated with the source name from the cache, if the file exists
        [DllImport(@"wininet",
            SetLastError=true,
            CharSet=CharSet.Auto,
            EntryPoint="DeleteUrlCacheEntryA",
            CallingConvention=CallingConvention.StdCall)]
        public static extern bool DeleteUrlCacheEntry(
            IntPtr lpszUrlName);

        public static void ClearCache()
        {
            // Indicates that all of the cache groups in the user's system should be enumerated
            const int CACHEGROUP_SEARCH_ALL = 0x0;
            // Indicates that all the cache entries that are associated with the cache group
            // should be deleted, unless the entry belongs to another cache group.
            const int CACHEGROUP_FLAG_FLUSHURL_ONDELETE = 0x2;
            // File not found.
            const int ERROR_FILE_NOT_FOUND = 0x2;
            // No more items have been found.
            const int ERROR_NO_MORE_ITEMS = 259;
            // Pointer to a GROUPID variable
            long groupId = 0;

            // Local variables
            int cacheEntryInfoBufferSizeInitial = 0;
            int cacheEntryInfoBufferSize = 0;
            IntPtr cacheEntryInfoBuffer = IntPtr.Zero;
            INTERNET_CACHE_ENTRY_INFOA internetCacheEntry;
            IntPtr enumHandle = IntPtr.Zero;
            bool returnValue = false;

            // Delete the groups first.
            // Groups may not always exist on the system.
            // For more information, visit the following Microsoft Web site:
            // http://msdn.microsoft.com/library/?url=/workshop/networking/wininet/overview/cache.asp			
            // By default, a URL does not belong to any group. Therefore, that cache may become
            // empty even when the CacheGroup APIs are not used because the existing URL does not belong to any group.			
            enumHandle = FindFirstUrlCacheGroup(0, CACHEGROUP_SEARCH_ALL, IntPtr.Zero, 0, ref groupId, IntPtr.Zero);
            // If there are no items in the Cache, you are finished.
            if (enumHandle != IntPtr.Zero && ERROR_NO_MORE_ITEMS == Marshal.GetLastWin32Error())
                return;

            int i = 0;

            // Loop through Cache Group, and then delete entries.
            while(true)
            {
                i++;
                if (i > 500)
                    break;

                // Delete a particular Cache Group.
                returnValue = DeleteUrlCacheGroup(groupId, CACHEGROUP_FLAG_FLUSHURL_ONDELETE, IntPtr.Zero);
                if (!returnValue && ERROR_FILE_NOT_FOUND == Marshal.GetLastWin32Error())
                {	
                    returnValue = FindNextUrlCacheGroup(enumHandle, ref groupId, IntPtr.Zero);
                }

                if (!returnValue && (ERROR_NO_MORE_ITEMS == Marshal.GetLastWin32Error() || ERROR_FILE_NOT_FOUND == Marshal.GetLastWin32Error()))
                    break;
            }

            // Start to delete URLs that do not belong to any group.
            enumHandle = FindFirstUrlCacheEntry(null, IntPtr.Zero, ref cacheEntryInfoBufferSizeInitial);
            if (enumHandle == IntPtr.Zero && ERROR_NO_MORE_ITEMS == Marshal.GetLastWin32Error())
                return;

            cacheEntryInfoBufferSize = cacheEntryInfoBufferSizeInitial;
            cacheEntryInfoBuffer = Marshal.AllocHGlobal(cacheEntryInfoBufferSize);
            enumHandle = FindFirstUrlCacheEntry(null, cacheEntryInfoBuffer, ref cacheEntryInfoBufferSizeInitial);

            i = 0;

            while(true)
            {
                i++;
                if (i > 500)
                    break;

                internetCacheEntry = (INTERNET_CACHE_ENTRY_INFOA)Marshal.PtrToStructure(cacheEntryInfoBuffer, typeof(INTERNET_CACHE_ENTRY_INFOA));		

                cacheEntryInfoBufferSizeInitial = cacheEntryInfoBufferSize;
                returnValue = DeleteUrlCacheEntry(internetCacheEntry.lpszSourceUrlName);				
                if (!returnValue)
                {	
                    returnValue = FindNextUrlCacheEntry(enumHandle, cacheEntryInfoBuffer, ref cacheEntryInfoBufferSizeInitial);
                }
                if (!returnValue && ERROR_NO_MORE_ITEMS == Marshal.GetLastWin32Error())
                {
                    break;
                }			
                if (!returnValue && cacheEntryInfoBufferSizeInitial > cacheEntryInfoBufferSize)
                {
                    cacheEntryInfoBufferSize = cacheEntryInfoBufferSizeInitial;
                    cacheEntryInfoBuffer = Marshal.ReAllocHGlobal(cacheEntryInfoBuffer, (IntPtr) cacheEntryInfoBufferSize);
                    returnValue = FindNextUrlCacheEntry(enumHandle, cacheEntryInfoBuffer, ref cacheEntryInfoBufferSizeInitial);					
                }
            }
            Marshal.FreeHGlobal(cacheEntryInfoBuffer);		
        }

        [DllImport("wininet.dll", SetLastError = true)]
        private static extern bool InternetSetOption(IntPtr hInternet,
        int dwOption, IntPtr lpBuffer, int lpdwBufferLength);

        public struct INTERNET_PROXY_INFO
        {
            public int dwAccessType;
            public IntPtr proxy;
            public IntPtr proxyBypass;
        };

        public static void RefreshIESettings(string strProxy)
        {
            const int INTERNET_OPTION_PROXY = 38;
            const int INTERNET_OPEN_TYPE_PROXY = 3;

            INTERNET_PROXY_INFO struct_IPI;

            // Filling in structure
            struct_IPI.dwAccessType =
            INTERNET_OPEN_TYPE_PROXY;
            struct_IPI.proxy =
            Marshal.StringToHGlobalAnsi(strProxy);
            struct_IPI.proxyBypass = Marshal.StringToHGlobalAnsi("local");

            // Allocating memory
            IntPtr intptrStruct = Marshal.AllocCoTaskMem(Marshal.SizeOf(struct_IPI));

            // Converting structure to IntPtr
            Marshal.StructureToPtr(struct_IPI, intptrStruct, true);

            bool iReturn = InternetSetOption(
                IntPtr.Zero,
                INTERNET_OPTION_PROXY,
                intptrStruct,
                Marshal.SizeOf(struct_IPI));
        }
    }
}